Neutralized cathode-ray deflection tube



Nov. 29, 1949 P. J. sELGlN NEUTRALIZED CATHODE-RAY DEFLECTION TUBE Filed Jan. 2o, 1947` INVENTOR PAUL J. SELGIN ATTORNEY momaom .329m

Patented Nov. 29, 1949 UNITED STATES PATENT `OFFICE NEUTRALIZED CATHODEHRAY DEFLECTIQN TUBE Paul J. Selgin, Fort Wayne, Ind., assignor, b y mesne assignments, to Farnsworth Research Corporation, a corporation of Indiana Application January V20, 1947, Serial No. 723,035

12 Claims. (CI.- Z50-#27) This invention relates to cathode ray tubes and particularly to devices of this character which are capable of operating substantially independ= ently of the influence of stray iields.

There are many cases in which it is dsirable to use cathode ray tubes for the purpose of signal generation and/or signal modulation. Devices capable of such uses, in general, comprise a cathA de ray tube wherein one or more electron beams are deflected over a target electrode of particular conguration under the control of intelligence signals. Heretofore, such devices have been particularly susceptible to the influence of Stray elds. As a result, the signals developed in the output circuit have contained spurious effects caused by the stray elds.

It has been proposed to employ an even number of electron beams, each of which is deflected over an associated target electrode structure in order to overcome the deleterious eiects of stray fields. Half of the beams have been deflected in one direction and the other half of the beams have been deflected in the other direction, all?- under the control of the signals. In this mannerI the undesired deflections of the beams caused by the stray elds have effectively been cancelled.

However, such structures are relatively cumbersome for the reason that generally they require the use ci separate apparatus for forming-:and deflecting the respective -beams over the target electrodes. Not only is such apparatus relatively` costly to produce, but also it is diiiicult to operatei Facilities must be provided for properly orienting. each of the electron beams relative to its associated delecting and target electrodes.

It, therefore, is an object of the present invention to provide a cathode ray tube structure, wherein initially a single electron beam is utilized to produce a plurality of beams for deflection, together with a relatively simple deecting and target electrode system, whereby to effectively neutralize the effect of stray elds upon the electron beam deections.

In accordance with this invention, there is provided a cathode ray tube having means for forining an electron beam and directing it toward a target electrode structure. Additionally, the tube is provided with facilities cooperating with a cle-4 flecting system, whereby the electron beam is effectively divided into two parts. The deilecting` system is operated in such manner that, under the control of intelligence signals, the two poritions oi the electron beam are deflected in opposite directions. provided and has a form suitable to collect` sub# A target electrode structure" is CFI,

stantially all of the electrons in the two b'eai'n portions so that, by connecting the target electrode structure to an output circuit, there are' developed signal effects representing only the electron beam deflections which are directly pro'- duced under the control of the signals. All beam deflections caused by the elects of stray magnetic or electrostatic fields are effectively cancelled in the output circuit. Additionally, the' tube may be provided with a metallic shield located so as to surround the space between the deflecting system and the" target electrode structure. Such :a shield provides additional shielding of the electron beam portions from stray electrostatic fields. More' importantly, however, the shield provides a sub= stantially field-free space between the deiecting system and the target electrode structure.

For a better understanding of the invention", together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the accompanying drawing:

Fig; 1 is a diagrammatic representation of a cathode ray tube having an electrode structure' which embodies the invention in an illustrative form, and

Figs.y 2', 3 and 4 are illustrations of typical rela@ tions'hips between the electron beam portions and the target electrode structure which are pros' duced under the control of the signals.

`I-Iaving reference now to Fig. 1 of the drawing, the cathode ray tube is provided with an vacue ated envelope I0. At the left hand e'ndV of the tube envelope there is provided an electron gun for developing an electron beam and projecting it generally towardy the right hand end of tlie tube; The electronl gun includes a cathode II which may be entirely conventional and which is c'ap`able of emitting copious quantities of electrons? when energized in any `suitable manner, such as by heating either directly or indirectly. In baclli of the cathode there is provided a repelling elect trode I2. In front of the cathode there is pro--K vided an accelerating anode electrode I3l whicl` has formed therein acentrally located aperture I4 in substantial alignment with the cathode. Preferably, the aperture I4 is provided with ci screen or grid structure I5, whereby to effectively nullify the lens elect which the aperture otherwise would have, and at the saine time', to permit the passage of the electrons through tlie` aperture. In the illustrated form of electron" gun, the accelerating anode' electrode I3- has the general form of an hyperbola and the repelling electrode l2 is formed in such a manner that the sides thereof are the asymptotes of the hyperbolic anode. In such a case the cathode II is located at the focal point of the hyperbola.

In front of the anode I3 there is located an electrode I6 which may be operated asA illustrated at the same potential as the accelerating anode. This electrode is located substantially at the center of the electron beam Il issuing from the anode aperture I4. Its purpose is to divide the beam Il into two substantially equal portions,= f

` the most positive point of the voltage supply sys- IIa and Ilb. It also functions in manner to be described to prevent electrons from striking one of the electrodes of the deflecting system.

In front of the beam separating electrode I6, there is provided a deilecting system which, in its illustrated form, comprises three substantially parallel plates I8, I9 and 20. The plates I8 and 20 constitute an external deflecting electrode structure which has a configuration suitable to form an aperture located in the paths of the electron beam portions Ila and I lb. The plate I9 constitutes an internal deflecting electrode structure which is located in the aperture of the external deflecting electrode structure substantially midway between the two beam portions.

l The deflecting plate I9 thus is located in sub- Stantial alignment with the beam separating electrode I6. Consequently, any electrons of the beam Il which otherwise might strike the deecting plate- I9 are intercepted by the electrode I6. Therefore, the center deecting plate I9 is not subject to potential variations as a result of electron impingement thereof.

Behind the deflecting system there is located a substantially cylindrical hollow metallic electrode 2|. This electrode is open at both ends and extends longitudinally of the tube along the central axes of the electron beam portions Ila and Hb. In some cases if desired, the shielding electrode 2I may be in the form of a metallic wall coating placed on the inside surface of the envelope I9. However, in the form disclosed, the shielding electrode may be employed advantageously for mounting some of the other electrodes of the tube in a manner to be described.

A target electrode system is provided adjacent the vother end of the shield 2| and, as shown, may include a pair of ilat plates 22 and 23 located in'substantial alignment at right angles to the electron beam portions. These electrodes do not extend-completely to the center of the tube, but instead provide a centrally located space through which all or a part of the electron beam portions may Pass. Additionally, there is provided a flat baiile plate electrode 24 in the space between the target electrodes 22 and 23 and which extends longitudinally of the tube substantially as shown. Finally, the target electrode system includes a ilat plate electrode 25 located in alignment with the space between the electrodes 22 and 23 substantially at right angles to the paths of the electron beams. The plates 22 and 23 constitute an electron intercepting electrode structure which has a configuration to form an aperture centrally located relative to the undeflected paths of the beams. The plate 25 constitutes an electron collecting electrode structure located behind the interceptor aperture.

f The various electrodes of the cathode ray tube, in accordance with this invention, as described, are' energized by connections to suitable sources of signals, power, etc; The power source for the tube electrodes is represented as a battery 26, the

tem as shown. The upper and lower deecting plates I8 and 29 respectively, the shielding electrode 2i, the target interceptor electrodes 22 and 23 and the baiile electrode 2t are all connected to a somewhat more positive point on the voltage divider than that to which the cathode I I is connected.

.-A signal source 28 is connected to the center deiiecting plate I9 and to a slightly more positive point on the voltage divider 2l than that to which the deii'ecting plates I8 and 29 are connected. This voltage divider point also is grounded. The target collector electrode 25 is connected through an output or load resistor 29 to the positive terminal of the voltage supply system. Finally there is provided a utilization circuit 3l connected across the resistor 29.

lReferring now to the operation of the cathode ray tube embodying this invention, the electron gun structure produces a single electron beam Il, which as described, is separated by the electrode I6 into two substantially equal portions Ila and I'Ib. In operating the device, the outer deilecting plates I9 and 2E! are maintained at a substantially constant potential, while the center plate I9 is operated at a potential which is varied in accordance with the signals impressed thereon from the source 28. Consequently, the upper portion I 'Ia of -the electron beam which passes between the deilecting plates I8 and I9 and the lower portion I 'Ih of the beam which passes between the deflecting plates -I9 and 29 are oppositely influenced by thevarying potential of the center plate. Dellectionsv of these two beam portions therefore are in opposite directions. The target electrode structure is. so arranged relative to the two electron beam portions that each of the beam portions at all times impinges both on the collector electrode 25 and on one of the interceptor electrodes 22 or 23. As these beam portions are deflected under control of the signals, the electron impingement of the interceptor and collector electrodes varies.

A better understanding of the behavior of the two beam portions in their relation to the target electrode structure may be had by reference to Figs. 2, 3 and 4. Fig. 2 illustrates the case where the signal voltage which is impressed upon the deecting system is zero. In this case there are substantially no deiiections of the electron beam portions. Approximately half of the upper beam portion Ila impinges upon the upper interceptor electrode 22 and the other half impinges upon the collector electrode 25. Similarly, the lower beam portion I'ib impinges in substantially equal magnitudes upon the lower interceptor electrode 23 and the collector electrode 25.

,Y The signal which is developed in the output circuit resistor 29 is dependent upon the electron collection by the electrode 25. Since approximately half of the electrons of each of the two beam portions is collected by this electrode, there is developed in the resistor 29 a voltage representative of this relationship between the elecaasaeco tron beam portions `.and the ltarget electrode structure.

Assume now that a signal of positive polarity is impressed upon the center deflecting electrode I9. The upper beam portion `I'Ia thereby is detlected downwardly and the lower beam portion I 1b is deflected upwardly. Fig. V3 illustrates the relation of these beamdeections to the target electrode structure. Both beam portions are deected toward the centrallongitudinal axis of the tube. In this case the major parts of both beam portions impinge upon the center collecting electrode 25 and only relatively small parts of the beam portions impinge upon the interceptor electrodes 22 and 23,.respectively. As a consequence a greater number of electrons are collected by the electrode -25 than in the case where the beam deections are effected by a zero signal voltage. The upper terminal of the output resistor 29 as a result develops a more negative potential. Since the lower terminal of this resistor is connected to a point of substantially constant potential, a negative voltage relative to the voltage representing a zero signal is developed in the output resistor for impression upon the utilization circuit 3 I.

If now a signal of negative polarity is impressed upon the center deflecting electrode I9, the upper beam portion I'Ia is deflected upwardly and the lower beam portion IIb is deflected downwardly. This condition is illustrated in Fig. 4. It is seen that the greater part of the beam portion Ila impinges upon the upper interceptor electrode 22 and only a small part impinges upon the collector electrode 25. Similarly the greater portion of the lower beam portion IIb impinges upon the lower interceptor electrode 23, while only a small part of this beam portion impinges upon the collector electrode. Consequently, in this case the electron collection by the electrode 25 is less than in the case of a Zero signal. As a result the upper terminal of the output resistor 29 becomes less negative, whereby to develop a positive output voltage in relation to the zero signal output voltage for impression upon the utilization circuit 3|.

Suppose that, externally of the tube, there exists a stray field of such a character that the electron beams tend to be deflected upwardly. Such a field will effect substantially the same magnitude of deflection of both beam portions. Considering first the upper beam portion I'Ia, it is seen that more electrons will be collected by the upper interceptor electrode 22 and less electrons by the center collecting electrode 25 than would occur if the beams were not subjected to the stray field. On the other hand, the upward deflection of the-other beam portion I'Ib by the external eld causes more electrons to be collected by the center collector electrode 25 and less electrons by the lower interceptor electrode 23. The result is that the loss of electrons from the upper beam portion I'Ia by the center electrode 25 is oiset by the gain of electrons by this electrode from the lower beam portion I'Ib. Consequently, the signal voltage developed in the resistor 29 is the sameas it would be if no stray eld were present.

It should be apparent that a device such as that described embodying the invention has several advantages over prior art cathode ray tubes of the deflecting modulation type. In the rst place, a single electron gun structure may be employed, with the attendant advantages of simplifying tube construction and power consumption. Also, the deflecting electrode structur wherein two deiiecting systems vare provided by the use of three electrodes has the advantage of relative simplicity of construction. The arrangement of such a deecting system enables the simultaneous deflections of ftwo beam portions in opposite directions. Such a facility enables the device to operate substantially independently of stray fields.

The tube, being provided with a shielding kelec-- trode 2|, also is advantageous for the reason that it simplies the Construction of the device. A great many cf the electrodes located at either end of the shield are electrically connectedthereto and at the same time may advantageously be mechanically attached to the shielding `electrode. Furthermore, others of the electrodes which may be operated at different potentials from the shield may also be supported mechanically thereby through the use of suitable insulating supports. Furthermore, the shield serves to provide additional protection for the electron beam from any external electrostatic stray iields. More importantly however, it provides a fieldfree space through which the electron beam mayl pass in the major portion 0I `its travel from the deiiecting electrode system to the target electrode structure. In this manner, as is well knownV in the art, tl-.e electrons maintain the directions imparted to them by the deflecting system.

It is also advantageous to employ the barrier electrode 2li in the aperture formed between the upper and lower interceptor electrodes 22 and v23 respectively. By maintaining the barrier electrode at a potential which is no higher than'that of the two adjacent electrodes, it serves to inhibit the emission of secondary electrons by thel adjacent electrodes. ln some cases it may be more desirable to impress a potential upfon the electrode 2li which is somewhat negative relative to .the electrodes 22 and 23. Inasmuch as the electron beam portions strike the target elec-- trodes with considerable velocity, there is a tendency to liberate secondary electrons from these electrodes. The presence of the barrier electrode 24 however, produces a field condition which overcomes this tendency for the liberation of secondary electrons. As iswell known in the art, where utilization is not made of secondary electrons, it is necessary to provide facilities for; collecting them in order to avoid -the introduc--g tion of spurious signal effects in the signal repre-:-

sentative voltages developed in the output circuit. It therefore is more convenient to inhibit the liberation of such secondary electrons than it is to permit them to be liberated and then to collect them.

However, a device in accordance with the pres-y ent invention may have incorporated therein an electron multiplier for functioning in conjunction with the target electrode structure. VIn such a case direct employment may be made of secondary electrons liberated by the impingement of the electron beam portions upon the target electrode structure. A barrier electrode, such as 24, would not be used in such an event. As many stages of electron multiplication as desired may be employed in any manner well known in the art. I

It also is considered to be within the scope of the present invention to couple the electrode structure of a tube embodying the invention to an output circuit in any well known manner other than that disclosed specifically herein for illustrative purposes. For example, it is obvious that 7' theelectronlimpingement ofthe interceptor elecil trodesf22f and 423 alsoifvariesflin accordancewith the'v'de'ections ofvthe'ilbeam portions under the control". of' the signals. Consequently; the intercepto'rlfelectrodes-l m'ay be 'coupled to an output circuitH-resistor,-suchfas the resistor 29,` instead ofthecollector electrode'25. In sucha case how- K ever'lthepOIarity of the voltages `developed in the output circuit resistor would be reversed from those des'cribed, since the electron impingement of thefvinterceptor electrodes is of opposite phase tc th'evelectronimpingement Vof the collector electrodea i Y' l JWhilethere-has been described what at presentisf. considered thelprefer'red embodiment of thelinvention, it will be obviousto those skilled inthe'art thatvarious changes'and modifications Inay be` made-therein without departing from the'- invention, and;v therefore, it is `aimed in the appendedclaims'to cover Aall such changes and modifications as fall within the true spirit and Scop'efof the invention;

What isf'cla'imedl is:` f ""lA "cathode ray tube comprising, means for developing two electron beam portions and for projecting said `beam portions toward a target electrode-system, an electron beam deflecting system located adjacent to said beam developing means'and comprising an external electrode structure and'an' internal electrode structure, said external deilecting electrode structure having a congurationto form an aperture located in thepaths of said beams, said internal deflecting electrode structure b eing located substantially caXia-lly with ysaid beam paths in the aperture ofisaid external electrode structure, said deflecti'n'g" electrode system functioningin response to varying potentials of opposite polarity on said internal and' external electrode structuresv respectively tov concurrently deflect both of said two beam portions in opposite directions, and a target electrode system located remote from said `de fleeting electrodesystem and including an'elec-l tron'interc'eptor electrode structure andan electron collecting'electrode, said interceptor electrode structure being arranged to form an apertiire centrally located*v relative to the undeflected paths of said two beam portions and said electron collector being located behind said interceptor aperture, whereby the deflections of said two electron beam portions oppositely vary the electron impingement upon said interceptor and said collector electrodes respectively.

2. A cathode ray tube comprising, means for developing two electron beam portions and for projecting said beam portions toward a target electrode system, an electron beam deflecting system located adjacent to said beam developing means and comprising three electrodes, two of said deecting electrodes being mounted on opposite sides of the paths of said beam portions and each being maintained at a substantially constant potential and the third one of said deflecting electrodes being located substantially coaxially with said beam path and subject to a varying potential of opposite polarity to the potential of said two deflecting electrodes, said delecting electrode system functioning to divide said electron beam into two portions which, under the control of the varying potentials impressed upon said third deecting electrode, are deflected concurrently in opposite directions, and a target electrode system located remote from said deflecting electrode system and including an electron interceptor electrode structure and an electron collecting .Ielec't'rode,saidliinterceptor elec trode structure having a form to definefan aperture centrally located `relativeto the 'undeiiected paths of'said two beamportionsfand said electron collector beinglocated behind said interceptor aperture; whereby the deections of said two electron beam portions oppositely vary the electron impingementuponsaid interceptor and said -col'- lector electrodes respectively in accordance with the potential variations of said third deflecting electrode.

'-3.v A cathode ray tube comprising, means for developing an electron beam and for projecting said` beam toward a target electrode system, a target electrode system' including an electron interceptor electrode structure and an electron col' l'ecting electrode mounted at right angles to the path of said beam, said electron interceptor electrode structure having a form to define an aper-` tu're symmetrically located relative to the center of'said beam path, said electron collector beingl located behind said interceptor aperture, and an electron beam deiiecting system located between said beam developing means and said target electrode system and comprising three electrodes mounted in mutually spaced relationship, the center one ci said delecting electrodes being lo cated substantially coaXially with said beam path and the outer defiecting electrodes being located on opposite sides of said beam path, a voltage variation between said center deflecting electrode and said outer delecting electrodes causing said beam' to converge and diverge, whereby to oppositely vary the electron impingement upon said interceptor and said collector electrodes respectively.

4.7' A cathode ray tube comprising, means forv developing an electron beam and for projecting said beam toward a target electrode system, a

target electrode system including three electrodes' mounted at right angles to the path of said beam, two of said electrodes constituting an electron interceptor being spaced apart symmetrically relative to the center of said beam path and the third electrode constituting an electron collector being located behind said interceptor electrodes in alignment with theA space therebetween, and an electron beam deflecting system located between said beam' developing means and said target electrode system and comprising three plates mounted in spaced planes parallel to the path of said beam, the center one of said deflecting plates being mounted substantially coaxially with said beam path and the outer dellecting plates being mounted on opposite sides of said beam path, a voltage variation'between said center delecting plate and said outer delecting plates causing said beam to converge and diverge, whereby to oppositely vary the electron impingement upon said' interceptor and said collector electrodes respectively.

v5. A cathode ray tube comprising, means for developing an electron beam and for projecting said beam toward a target electrode system, a target electrode system' including three plates mounted at right angles to the path of said beam, two of said plates constituting an electron interceptor being spaced apart symmetrically relative to the center of said beam path and the third plate constituting an electron collector being located behind said interceptor plates in alignment with the space therebetween, an electrode located in the space between said interceptor plates for inhibiting secondary electron emission by said interceptor plates, and an electron beam deectf absaeso `ing system located between said beam developing means and said target electrode system andcomprising `three plates mounted in equally spaced planes parallel to the path of said beam, the'center one of said deflecting plates being mounted substantially coaxially with said beam path .and the outer deflecting plates being electrically. interconnected and mounted on opposite" sideslof said beam path, a voltage variation betweensaid center deflecting plate and said outer` delecting plates causing said beam to converge and diverge, whereby to oppositely vary the electron impingement upon said interceptor and said collector plates respectively.

6. A cathode ray tube comprising, means for developing an electron beam and for projecting said beam toward a target electrode system, a target electrode system including three substantially flat plates mounted at right angles .to the path of said beam, two of said plates constituting an electron interceptor being spaced apart symmetrically relative to the center of. said beamgpath and the third plate constitutingan electr-on .collector being located behind said interceptor plates in alignment with the space therebetween, an electrode located in the space between said interceptor plates for inhibiting secondary electron emission by said interceptor plates, an electron beam deflecting system located between said beam developing means and said target electrode system and comprising three substantially flat plates mounted in equally spaced planes parallel to the path of said beam, the center one of said deflecting plates being mounted substantially coaxially with said beam path and the outer dellecting plates being electrically interconnected and mounted on opposite sides of said beam path, a voltage variation between said center delecting plate and said outer delecting plates causing said beam to converge and diverge, whereby to oppositely vary the electron impingement upon said intercepwr and said collector plates respectively, and a hollow substantially cylindrical shield surrounding said electron beam between said deilecting and said target electrode systems.

7. A cathode ray tube comprising, an evacuated envelope, an electron gun located adjacent one end oi said envelope for projecting an electron beam toward the opposite end of said envelope, means including an electrode located adjacent to said electron gun for dividing said beam into two portions a dellecting structure for each of said beam portions including a plurality of parallel spaced plates, one of said plates being common to both deflecting structures, whereby said beam portions concurrently are deflected oppositely in response to signal voltage impressed upon said deflecting structures, a pair of electron interceptor plates located partially in the respective paths of said beam portions adjacent the opposite end of said envelope, an electron collector electrode located partially in the paths or" both of said beam portions, and an electrostatic shield surrounding the space between said deilecting structure and said interceptor electrodes.

8. A cathode ray tube comprising, an evacuated envelope, an electron gun located adjacent one end of said envelope for projecting an electron beam toward the opposite end of said envelope, an electrode located in said electron beam path adjacent to said electron gun for dividing said beam into two portions, a deflecting structure for each of said beam portions comprising three substantially parallel spaced plates, the center one of said 10 plates being common to both delecting structures, whereby said beam portions concurrentlj7 are deected oppositely in response to a signal voltage impressed symmetrically upon both delecting structures, a pair of spaced electron interceptor plates located respectively in the paths of said beam portions adjacent the opposite end of said envelope, an electron collector electrode located in alignment with the space between said interceptor plates in the paths of both of said beam portions, and a metallic shield surrounding `the lspace between said deecting structure and said interceptor electrodes. l 9. A cathode ray tube comprising, an evacuated envelope, an electron gun located adjacentone Lend of said envelope for projecting an electron beam toward the opposite end of said envelope,.an electrode located at the center of said electron beam path adjacent to said electron gun ior` dividing said beam into two substantially equal por,- tions, a deilecting structure for each of said beam portions comprising three substantially parallel 'spacedplates the center one of said platesbe: ing common to both deilecting structures, whereby said beam portions concurrently are deflected oppositely in response to a signal voltage impressed upon said center plate, a pair of spaced electron interceptor plates located respectively in the paths of said beam portions adjacent the opposite end of said envelope, an electron collector electrode located behind the space between said interceptor plates in the paths of both of said beam portions, and a hollow metallic shield surrounding the space between said deflecting structure and said interceptor electrodes.

10. A signaling system comprising, a source of signals, a cathode ray tube having means including an electron gun for developing an electron beam divided into two portions, a deecting electrode structure for each of said beam portions comprising a plurality of spaced electrodes located adjacent the respective paths of said electron beam portions, two of said deflecting electrodes being associated individually with said respective beam portions and a third one of said deflecting electrodes being associated with both of said beam portions, a target electrode structure located in the paths of said beam. portions including a pair of electron interceptor electrodes and an electron collector electrode, said interceptor electrodes being located in the respective paths of said beam portions and said collector electrode being located in the paths of both of said beam portions, electrical connections between said two deilecting electrodes associated individually with the respective beam portions, means for coupling said signal source between said third deiiecting electrode commonly associated with both of said beam portions and said interconnected deflecting electrodes, an output circuit, and means for coupling said target electrode structure to said output circuit.

11. A signaling system comprising, a source of signals, a cathode ray tube having an electron gun for projecting an electron beam, means located adjacent said electron gun for dividing said beam into two portions, a deflecting electrode structure for each of said beam portions comprising a plurality of parallel spaced plates located adjacent the respective paths of said electron beam portions, a target electrode structure located in the paths of said beam portions and including a pair of spaced electron interceptor plates and an electron collector plate located in alignment with the space between said intercep- 11 `tor plates, a metallic shielding electrode enveloping thespace between said deflecting structure vand said target electrode Structure, electrical connections between the two outside ones of said deflecting plates, means for coupling said signal source between said center deecting plate and said interconnected outside deecting plates, an output circuit including a load impedance device, and means for coupling one of said target. velectrodes to said impedance device. v i

12. A signaling system comprising, a source of signals, a cathode ray tube having an electron gun for projecting an electron beamV towardja targetelectrode structure, means located 'in the path of saidbeam adjacent said Yelectron gun' for dividingA ,said beam into two portions', a deflecting electrode structure for each of said .beam portions comprisingthree substantially parallel spaced plates located adjacent the respective pathsjpf said electron beam portions, a targetlelectrode `structure including a pair of spaced electron interceptor plates and an electron collector plate in back of said interceptor plates and in :alignment with the space between `said* intercepy PAUL J. SELGIN.

REFERENCES CITED vk", MIne `following references are of record in the le ot this patent:

UNITED STATES PATENTS Number Name Date 12,077,271 Schlesinger Apr. 13, 1937 `l"2,083,204 Schlesinger June 8, 1937 "2,089,692, Drewang Aug. 10, 1937 A1,214,019 Gray Sept. 10, 1940 

